error handling in file.inc's file_check_upload doesn't work

Hi,

this is pretty much the same issue as has been identified in Drupal 6.x here: http://drupal.org/node/248185

...this leads to the silent failure of file uploads where the file is too big, or another error occurs (http://php.net/manual/en/features.file-upload.errors.php)

The code effectively checks to see if a file has uploaded successfully (checked using is_uploaded_file function) before it tries to do any error handling - however, if there's an error (including the file being too big for the environment) the file doesn't upload successfully, and so the error handling code never runs.

A patch which fixes this (and adds some logging if the uploaded file fails the is_uploaded_file test) is attached - the patch is ugly to look at, but mainly involves just moving the order of things around a little.